The present invention relates generally to a shipping container coupling and more particularly pertains to a very simple and safe manually operated container hook design.
The use of shipping containers has gained almost universal acceptance in the inter-modal movement of cargo throughout the world. The containers are alternately trucked, shipped, hauled or stored without the need to handle the cargo therein. Fully laden containers are simply lifted onto a trailer truck, rail car, freighter deck, placed in a freighter hold or efficiently stacked in storage yards.
Such containers are provided with cast lift fittings at each corner by which the containers may easily be grasped and lifted. The lift fitting normally includes a standardized hollow cubic structure formed with a cavity and having an elongated slot in its top wall. A variety of hook designs are capable of engaging this type of lift fitting. Generally an elongated coupling hook is lowered through the slot into the interior of the fitting where it is subsequently rotated to a position transverse to the length of the slot. Various methods of locking the elongated hook in this position are subsequently employed which then allows the container to be safely lifted.
In order to expedite the process of engaging and lifting the containers, rigid overhead spreaders are generally suspended from a crane for disposition over the container to locate four hooking devices disposed in vertical alignment over the respective slots. After insertion into the respective lift fittings, the hooks are automatically rotated into a transverse position relative to the elongated slots to be locked into place.
When an automatic container spreader is unavailable or, if a shipping container has been badly damaged or is wracked out of square thereby precluding the use of an automatic spreader, a set of four manually operated hooks can be used to engage and hoist the container by the lift fittings. In addition, it sometimes becomes necessary to use manually operated hooks when the containers are awkwardly positioned or jammed within the below deck cells of a container vessel.
The prior art provides a number of designs adapted for such manual engagement of a container's lift fittings. Representative examples of varying complexity are described in Wilner U.S. Pat. No. 4,068,878, Lombardi U.S. Pat. No. 3,845,527 and Varadi U.S. Pat. No. 4,139,228. All three designs employ moving parts to fulfill the functions of engaging and locking onto a lift fitting. The use of moving parts adds to the cost of manufacture and normally requires at least some maintenance. In addition, moving parts are susceptible to becoming jammed and can malfunction thereby preventing either proper engagement or disengagement with a container. The use of rather delicate parts in the design described in Varadi renders the device especially prone to failure and in need of maintenance.
Shields in U.S. Pat. No. 3,792,892 describes a lifting hook, which, although extremely simple in design, presents a number of disadvantages in its function. As was indicated above, it is often necessary to extract containers jammed into below deck cells, oftentimes positioned at extreme angles or inclinations. It is possible that, upon engagement with the lifting hook described in this patent the container could shift and roll to angles which would allow the hooks to disengage. In addition, a slackening of the cables while manipulating a container can similarly allow a hook to disengage. Furthermore the described design precludes movement of the hooks in a plane perpendicular to the container's grasped surface thereby causing undue strain to be applied to the hook and the hoist cable, if the attached container is positioned in or moves through an extreme angle relative to the horizontal.